The use of fragrance to provide a pleasing scent to freshly dried fabrics as well as to modify or enhance the fragrance of fabric conditioning articles is both desirable and well known in the art as illustrated in U.S. Pat. No. 4,954,285 issued to Wierenga et al. However, the efficient deposition of such perfumes on fabrics as well as the manufacturing of fabric conditioning articles has not been achieved to date. The volatile perfumes tend to be lost during manufacturing of the tumble drier sheets as well as during their storage and use by the consumer. Various techniques have been tried in the prior art to address these problems. In general, these techniques involve entrapping the volatile fragrance oil with a coating or by mixing the oil with a suitable carrier.
Solid fragrance particles have also been prepared by mixing and absorbing the fragrance oil with a solid carrier to deliver fragrance to a product.
In U.S. Pat. No. 4,152,272 particles are formed from a perfume/wax mixture. The resulting particles are primarily incorporated into an aqueous fabric conditioner composition. This type of perfume/wax particle is undesirable for the manufacture of such particles into a tumble drier sheet because the molten fabric softener actives deposited on the sheets reach temperatures of up to 80.degree. C. Such manufacturing temperatures would cause the majority of the perfume containing particles with melting points below the processing temperature to melt releasing the majority of the fragrance during manufacturing of the sheets rather than being deposited on the drying fabrics. For those wax/perfume particles having melting points above the processing temperature the perfume is extracted by the molten active softener material.
In U.S. Pat. Nos. 4,954,285; 4,536,315 and 4,073,996 perfumed oils are mixed and absorbed with an inorganic carrier such as clay or silica to deliver perfume in detergents and fabric softeners. In U.S. Pat. No. 4,326,967 and EP 334,666 perfumes are emulsified in a wax or solid surfactant and the fragrance oil is released during heat treatment such as in a drier.
A fragrance containing polymer incorporated in detergent compositions comprising a water soluble polymer, a water insoluble polymer and a perfume composition which is part of both the water soluble and water insoluble polymers is described in U.S. Pat. No. 4,842,761. The two polymers are physically associated with each other so that one polymer forms discreet entities in the matrix of the other polymer.
In general, although these free flowing solid particles provide for the controlled release of the oil fragrance, the fragrance oil is generally not sufficiently protected so that it is frequently lost or destabilized during processing. It is also difficult to extract the fragrance when desired during use.
In U.S. Pat. No. 4,842,761 the perfume capsules largely depend on increasing size to increase the amount of deposited on clothes or fabrics and compensate for perfume lost during processing. Additionally, the particles require a large amount of water (e.g. wash or rinse liquor) to release the fragrance oils. Thus, the polymer matrix of the '761 patent would not effectively deliver fragrance at the end of the drying cycle as claimed in the subject invention.
Specifically, water dispersible polymers have been used to encapsulate fragrance oils in conventional spray drying processes as described in U.S. Pat. Nos. 4,276,312; 3,971,852; 3,821,436; 3,758,323; 3,455,838; 3,159,585 and 3,091,567. Such solid particles are made by emulsifying fragrance oils into an aqueous solution of the water dispersible polymer such as gum arabic, starch or gelatin. The emulsion is then sprayed into a column of hot air to yield free flowing microcapsules with the oil entrapped or encapsulated inside the water soluble polymer. Such spray drying techniques have been widely employed to make encapsulated fragrance particles. However, the conventional processes are not suitable for manufacturing the claimed composite microcapsule because large aggregates of perfume wax mixture are formed in the emulsion solution and can not be spray dried.
It is thus an object of the invention to provide fragrance encapsulated particles which will prevent the release and loss of the majority of the fragrance oil during processing, storage and use of fabric conditioning articles and which will release the majority of the fragrance onto drying fabrics.
Additionally, the fragrance particles may be incorporated in a fabric softening composition and applied to a dispensing means to produce an article for use in automatic clothes dryers to condition fabrics.
Another object of the invention is to provide a novel process for forming the claimed microcapsules to avoid loss of fragrance oils during processing, storage and use.